The present invention generally relates to an optical system that facilitates laser capture microdissection techniques.
Many diseases are identified by examining tissue biopsies to identify unusual cells. Examples include cancer. One problem with examining such tissue biopsies is that there is room for improvement in extracting the cells of interest from the surrounding tissue. Currently, investigators must attempt to manually extract, or microdissect, cells of interest either by attempting to mechanically isolate them with a manual tool or through a convoluted process of isolating and culturing the cells. These approaches can be tedious, time-consuming, and/or inefficient.
A new technique that extracts a small cluster of cells from a tissue sample in a matter of seconds is gaining attention. The technique is called laser capture microdissection. Laser capture microdissection is a straight forward technique which integrates a standard laboratory microscope with a low-energy laser and a transparent thermoplastic film.
Laser capture microdissection involves providing a tissue sample typically on a slide under observation in a microscope. The tissue is contacted with a selectively activated surface which could be activated to provide selective regions thereof with adhesive properties. The tissue sample is visualized through the microscope and at least one portion of the tissue sample which is to be extracted is identified. Thereafter, the selectively activated surface is activated, typically by a laser routed through a fiber optic being directed onto the selectively activated surface in the footprint of the desired tissue. This is done while a region of selectively activated surface is in contact with the portion of the tissue sample selected. The activated region of the selectively activated surface adheres to that portion of the tissue sample. The activated surface is then separated from the tissue sample while maintaining adhesion between the activated region of selectively activated surface and the portion of the tissue sample. The portion of the tissue sample is extracted from the remaining portion of the tissue sample.
One purpose of the laser capture microdissection technique is to provide a simple method for the procurement of selected human cells from a heterogeneous population contained on a typical histopathology biopsy slide. By taking only these target cells directly from the tissue sample, scientists can immediately examine the target cells. Moreover, gene and enzyme activity of the target cells can be analyzed using other research tools. In this connection, procedures such as polymerase chain reaction amplification of DNA and RNA, and enzyme recovery from the tissue sample are useful. No limitations currently exist in the ability to amplify DNA or RNA from tumor cells extracted with laser capture microdissection.
Currently available optical systems or microscopes are not well suited for facilitating laser capture microdissection. For example, currently available optical systems have narrow fields of view, small depth of field, and small working distances under high magnification. The narrow field of view makes it difficult to identify a precise location for irradiation. The small depth of field makes it difficult to monitor the progress of irradiation. The small working distance makes it difficult to manipulate and handle the tissue sample.
Many microscopes are designed to provide images of certain quality to the human eye through an eyepiece. Connecting a Machine Vision Sensor, such as a Charge Coupled Device (CCD) sensor, to the microscope so that an image may be viewed on a monitor presents difficulties because the image quality decreases, as compared to an image viewed by a human eye through an eyepiece. As a result, optical systems for laser capture microdissection often require the careful attention of a technician monitoring the process through an eyepiece.
The direct access to cells provided by laser capture microdissection may lead to improvements in the understanding of the molecular basis of cancer and other diseases, helping to lay the groundwork for earlier and more precise disease detection. The optical system and methods of the present invention furthers this understanding by enabling at least one of finer and more precise laser capture microdissection tissue sampling; greater working distances thereby not interfering with manipulation of the tissue samples; flexibility in laser spot positioning and sizing; closed circuit, web based, and remote monitoring of laser capture microdissection procedures; immediate examination of tissue samples; and automated process control of laser capture microdissection systems and methods.